Process for reacting ketene and hydrocyanic acid



mutant. 5,

PA ENT -orrics HYDBOCYANIO ACID Franklin Johnston, St. Albans, and Lawrence W. Newton, South Charleston, W. Va., assignors to Carbide and Carbon Chemicals Corporation, a corporation of New York -No Drawing.

Claims.

This invention relates to the production of organic derivatives'of hydrocyanic acid; and more especially it concerns the production of such derivatives by reactions involving hydrocyanic acid and ketene in the presence of a small amountof.

a basic condensation catalyst or reaction pro- ..moter of the type hereinafter described. The invention has especial utility for the production from ketene and hydrocyanicacid of l-cyanovinyl acetate and/orthe dimer of acetyl cyanide commonly designated dimolecular acetyl cyanide.

In the past l-cyanovinyl acetate has been pro-- duced'experimentally in the laboratory in small yields of less than by mixing ketene with twice its volume of anhydrous hydrocyanic acid in a sealed pressure tube at temperatures below 0? C., and shaking themixture while it is allowed to come to room temperature. The resultant reaction products included diketene, dehydracetic acid and various resinous polymerization products. The reaction was conducted in the absence of catalysts and of solvents for the reactants.

Dimolecular acetyl cyanide has heretofore been produced (1) by reacting hydrocyanic acid with acetic anhydride at about 200 C.; (2) by treating acetyl cyanide with metallic'sodium'; and (3) by reacting potassium cyanide in benzene solution with acetic anhydride.

The present invention is based in important part upon the discovery that l-cyanovinyl acetate and/or dimolecular acetyl cyanide can be produced'in good, yields by reacting ketene and dry hydrocyanic acid, preferably in the proportions of from 2 to 3 mols of the former per mol oi the latter, at temperatures within the range between about ---50 C. and about 30 C., in the presence of..a basic catalyst or reaction promoter which does not react with ketene to form non-basic .products under the conditions oi: the aforesaid reaction. 7

Our experiments lead to the conclusion that basic substances in general are effective catalysts for the reaction, provided, of course, that they remain basic under the conditions of the reaction. Thus a basic substance is suitable unless it reacts with ketene to form a non-basic-product. Tertiary amines are suitable because they do not react readilywithketene at the temperatures used in this invention, but ammonia, primary, and secondary amines are less desirable or useless because they react readily with ketene, forming non b'asic amides. Sodium hydroxide is suitable, although it reacts with ketene, because sodium acetate, so iormed,' is basic, whereas calcium hydroxide has little or no value in the pres- Appllcation February 12, 1944,- Serial No. 522,174

out invention, because calcium acetate is not basic, at least as this term is commonly employed, and any basicity which it may have is too little to be of practical value in the present invention.

do not react with ketene to form non-basic products and have found that all such substances which we have tried catalyze the reaction. Among basic substancesv which function eflecl9 tively to catalyze the reaction may be mentioned the tertiary aliphatic and aromatic amines; the quaternary ammonium bases; the alkali metal hydroxides, alkoxides, aryloxides, amides and cya- 1 nides; and the alkali metal salts of organic and 15 weakinorganic acids. Examples of such reaction promoters include triethyl amine, triethanolamine, pyridine, tetraethanolammonium hydroxide; trimethylbenzylammonium hydroxide, sodium and potassium hydroxides, sodium methylate, po-

tassium ethylate, and sodium alcoholates derived The mechanism of the reactions forming the' dimer of acetyl cyanide is probably as followsz upon neutralization of the reaction mixture from the catalyzed reaction may be:

' Among catalysts suitable for use with the in- We have tried many basic substances which other fatty acids, sodium carbonate, potassium vention may be mentioned such tertiary amines as triethylamine, triethanolamine, triisopropanolamine, pyridine, the N-substituted morpholines such as N,2-cyanoethyl morphollne, etc. The quaternary ammonium bases may include compounds of the type NRR R R OH wherein R, R R." and R respectively, may be the same alkyl or aryl radical, or different alkyl or aryl radicals. Examples are tetraethylammonium hydroxide, tetraethanolammonium hydroxide, and trimethylbenzylammonium hydroxide.

In accordance with the invention, ketene is condensed with dry hydrocyanic acid, at temperatures between about -50 C. and about +30 C., and preferably at temperature within the range between about 20 C. and about C., in the presence of a small amount of a basic catalyst such as those of the type hereinbefore described. The use of the higher temperatures, for example those around 10 C. to 30 C., favors the production of the acetyl cyanide dimer.

The condensation reaction preferably is conducted in the presence of an anhydrous volatile organic solvent or diluent for the reactants and the catalyst. A suitable solvent desirably is one that is inert to the reactants and to the catalyst;

however, ,even solvents containing active groups, such as acetone and methyl acetate, are successfully used. Among solvents advantageously employed in the process may be mentioned organic acid anhydrides such as acetic anhydride; the aliphatic others, such as diethyl ether and dioxane; esters of carboxylic acids such as methyl acetate, ethylacetate and l-cyanovinyl acetate;

ketones such as acetone; and mixtures of one or more of these solvents with acetic anhydride.

The use of acetic anhydride alone as a solvent or diluent in the reaction mixture is particularly advantageous and tends to provide almost quantitative yields of the l-cyanovinyl acetate. When used in conjunction with other volatile solvents or with inert diluents, about 10% by weight of the acetic anhydride conveniently may be employed. l-cyanovinyl acetate may be used effectively as the solvent or diluent; and especially good results are secured when using as solvent a mixture containing that compound mixed'with from about 10% to 20% of its weight of acetic anhydride. Similarly, an excess of hydrocyanic acid may be employed, in which case the excess acid functions as a volatile solvent or diluent.

The condensation reaction between the ketene and hydrocyanic acid may be effected by slowly introducing a stream of ketene vapors into an agitated body of anhydrous hydrocyanic acid which contains the catalyst, and which preferably is in solution in a volatile solvent for the reactants and catalysts.

After the absorption of the requisite amount of ketene, the reaction mixture may be fractionally distilled under subatmospheric pressure in a suitable column still. The l-cyanovinyl acetate and/or the dimolecular acetyl cyanide, and any unreacted hydrocyanic acid and volatile solvent, are separately recovered.

The ketene and hydrocyanic acid may very advantageously be introduced concurrently, preferably in a ratio of between 2 and 3 mols of the former to one mol of the latter, into a solution of the catalyst in a volatile solvent for the reactants.

The resultant reaction mixture, after absorption of the required amount of ketene, is fractionally distilled under vacuum in the manner previously indicated for the isolation and recovery of the decyanic acid and solvent.

By neutralizing the condensation reaction mix- Example 1 One hundred and seventy eight grams of ketene were slowly introduced into 81 grams of anhydrous hydrocyanic acid containing 3 cc. of pyridine as catalyst, while maintaining the mixture of reactants at about 20 C. After absorption of the ketene was completed, the reaction mixture was fractionally distilled under vacuum through a short column. A 36% yield of l-cyanovinyl acetate was secured as a fraction boiling at between 104 and 107- C. under an absolute pressure of 100 mm. of mercury, and was separately recovered. A yield of 32% of dimolecular acetyl cyanide also was recovered as a fraction boiling at C. under an absolute pressure of 4 mm. of mercury.

Example 2 Following the general procedure described in Example 1, 295 grams of ketene were introduced into a mixture of 81 grams of anhydrous hydrocyanic acid, 3 cc. of triethylamine and 300 cc. of anhydrous diethyl ether, while maintaining the reaction mixture at -50 C. Fractional distillation of the resultant reaction mixture under vacuum resulted in the recovery of a yield of 50% of l-cyanovinyl acetate as a fraction boiling between 104 and 107 C. under an absolute pressure of mm. of mercury, and a yield of 41% of dimolecular acetyl cyanide as a fraction boiling 'at 80 C. under an absolute pressure of 4 mm. of

Example 3 During a 4.5 hours period, 226 grams of ketene were slowly introduced into a mixture of 300 cc. of anhydrous diethyl ether, 81 grams of hydrocyanic acid and 1 cc. of triethylamine, maintained at a reaction temperature of about 0 C. The reaction mixture and basic catalyst were then neutralized by adding thereto one gram of glacial acetic acid. The neutralized reaction mixture was then fractionally distilled under vacuum in the general manner described in Example 1, yielding 149 grams of dimolecular acetyl cyanide and 27 grams of l-cyanovinyl acetate, corresponding to yields, respectively, of 72% and 8%.

Example 4 Example 5 Ketene and anhydrous hydrocyanic acid were are based I I concurrently introduced slowly over a. period of about two hours into 800 cc. of acetic anhydride containing- 3 can! triethanolamine and maintained at C. From 296 grams of ketene and 81. grams of hydrocyanic acid there were obtained 5 upon fractional distillation of the resultant re action mixture 289 grams of l-cyanovinyl acetate'and grams 0! dimolecular acetyl cyanide,

corresponding to yields oi 8'l% and 5%. of these products, respectively.

i Example 6 Ketene and anhydrous hydrocyanic acid were I concurrently introduced into a mixture 01 300 cc. of acetic anhydride containing 1 cc. of tri- 16' ethanolamine maintained at temperatures rangv ing from 22 to 31 C. From 264 grams'oi ketene and 81 grams of hydrocyanic acid introduced over a periodoi flve hours, there were secured,

ture, a 65% yield of l-cyanovinylfaceitate and a 28% yield of dimolecular acetyl cyanide.

Under similar operating conditions but using 3 cc..oi the triethanoiamine, and methyl acetate as the solvent, somewhat lower yields oi l-cyano- Example 7 Ketene and anhydrous hydrocyanic acid were concurrently introduced slowly over a period of about three hours into a mixture of 266 grams oi l-cyanovinyl acetate, 34 grams ofacetic anhy- 35- dride and 1 cc. oi'triethanolamine, while maintaining the mixture of reactants at 0 C. Upon fractional distillation under vacuum 01 the reaction mixture thus obtained from 269 grams of ketene and 81 grams of hydrocyanic acid, 540 grams 40 01 l-cyanovinyl acetate were recovered, establishing that 274 grams thereof had been produced in the process. This corresponds to a yield oi 82%'thereoi. Seven grams of unreacted hydrocyanic acid were recovered.

' Example 8 One hundred and ninety seven grams of ketene and 54 grams of anhydrous hydrocyanic acid were slowly added over a period of one hour to a mix- .ture of 250 cc. of ethyl ether, 30 cc. of acetic anhydride and 1' cc. of vtetraethanolammonium hye droxide maintained at 5 C. Fractional distillation of the resultant reaction mixture under vacuum in the general manner described in Example 55 1 yielded i-cyanovinyl acetate in amount corresponding to a yield of 98%. v

Under generally similar operating conditions but using 1 cc.- of trimethylbenzylammonium hydroxide as the catalyst, a somewhat lower yield 01 l-cyanovinyl acetate was secured.

, Example 9 Ketene and anhydrous hydrocyanicacid were 1 gram of sodium methylate maintained at -5 C. The reaction mixture was fractionated in the manner indicated inv Example 1. From 226 grams of ketene and 54 grams of hydrocyanic acid there but using sodium phenate as the catalyst, similar results are obtained.

During a period of 1.25 hours, 211 grams of ke-' tene and 54' grains of anhydrous hydrocyanic acid were added in small increments to a solution 01' 250 cc. ethyl ether, 30 cc. acetic anhydride, and 3 grams of sodium amide, maintained at -3 C. A yield of 83% of l-cyanovinyl acetate was obtained by fractional distillation of thereaction mixture.

, Example 11 Fi'ity iour grams of dry hydrocyanicacidwere added dropwise during 1.25 hours toja mixture of 250 cc. of ethyl ether, 30 cc. of acetic anhydride and 3 grams of potassium acetate maintained at 4 C., while passing. 259 grams oi'ketene into the mixture. Distillation oi the, crude reaction mixture yielded 85% of l-cyanovinyl acetate. 111-,

ternatively, potassium hydroxide 'may replace tassium acetate as the added atal st with upon fractional distillation of the reaction mix- 20 :gm results. Y.

. Erample 12.

During 2.5 hours 345 grams of ketene and 81 grams'oi dry hydrocyanic acid were added to a mixture of 300 cc. of ethyl ether, and 6 cc. of

N,2-cyanoethyl morphoiine maintained at approximately 45 0. Fractional distillation of the resultant reaction mixture gave a 75% yield oi l-cyanovinyl acetate and 9.8% yield of. di-

molecular acetyl cyanide. v v

Example 13 During a period of one 1101112197 grams oi ketene and 54 grams of dry'hydrocyanic acid were added to a mixture'oi 250 cc. 0! ethyl ether, 30 cc.

of acetic anhydride and one gram of potassium cyanide maintained at 5- C; The'resultant reaction mixture upon distillation gave a yield oi 71% of l -cyanovinyl acetate; I Example.

Under substantially the same conditions described-in Example 9, but substituting 3 grams of potassium naphthalene for the one gram of sodiacetate was secured. I

'1Yhe preparation of potassium naphthalene and similar alkali metallatesis described in Journal um methylate; a yield of 54% of 1- cyanovinyl 'oithe American Chemical Society, volume 58, page 2442.; and in United States Patent No.-

The results of extensive experimental work hasestablished that neither l-"cyanovinyl acetate nor dimolecular acetyl cyanide can be produced by'reacting ketene and hydrccyanic acid in the;

' distillation of the reaction mixture. Incr a in slowly added over 1.5 hours .to a mixture oi 250 05 e s g cc. of ethyl ethe'r, 3000. of acetic anhydride and the amount ofketene used and the time for the reaction did not change this'result. (Compare the catalyzed reaction of Example .5.) y

The l-cyanovinyl acetate produced by this invention -is a water-white, mobile liquid with a sharp'odor. It boilsbetween 104 107 C. under an absolute pressure of mm. of mercury; and

has a'speciiic gravity at 20/20 C. or 1.063; and a 1 refractive index at 20 C. of 1.;1253.

The dimolecular acetyl cyanideis a white, I crystalline solid melting at 70 C. to form a liquid which boils at 76-7790. under an absolute pressure of 3 mm. oi mercury.

preparation oi unsaturated cyanides, and of certain amines and di'basic organic acids.

The invention is susceptible of modification within the scope of the appended claims.

Wei claim: V

1. Process which comprises introducing successive portions of ketene into a liquid body maintained at a temperature within the range between about -50 C. and about +30 C.. and containing dry hydrocyanic acid and a basic condensation catalyst which under the conditions of the condensation does not substantially react with ketene to form non-basic reaction products, and recovering from the resultant reaction mixture at least one member of the group consistin of l-cyanovinyl acetate and dimolecular acety v cyanide present therein.

The dimo ecular acetyl cyanide has apparent value in the rently introducing successive portions of ketene and dry hydrocyanic acid in the ratio of between 2 and 3 mols of the ketene per mol of the said acid into a solution of a basic alkali metal compound in an anhydrous volatile solvent for the ketene and hydrocyanic acid; which basic compound does not substantially reactwith ketene I to form non-basic reaction products under the conditions of the resultant reaction between the ketene and hydrocyanic acid, said solution being maintained at a temperature within the range between about '50 C. and about 0 0., and

- separately recovering from the resultant reacbetween around 50 C. and around 0., i

and recovering from the resultant reaction mixture at least one member of the group consisting of l-cyanovinyl acetate and dimolecular acetyl cyanide.

3. Process which comprisesintroducing successive portions of ketene into-a liquid body containing dry hydrocyanic acid, a quaternary ammonium base, and an anhydrous volatile solvent for the reactants, and maintained at a temperature between around --50 C. and around +30 C., and recovering from the resultant reaction mixture at least one member of the group consisting. of l-cyanovinyl acetate and dimolecular acetyl cyanide.

4. Process which comprises introducing successive. portions of ketene into a substantially dry liquid body maintained at a temperature between around 50 C. and 0 C., and containing substantially dry hydrocyanic acid, a basic condensation catalyst which under the conditions of the condensation does not substantially react with ketene to form non-basic reaction products, and an anhydrous volatile solvent for the reactants, and recovering from the resultant reaction mixture at least one member of the group consisting of l-cyanovinyl acetate and dimolecular acetyl cyanide thereby produced.

5. Process as defined in claim 4 .wherein the solvent comprises acetic anhydride.

6. Process which comprises slowlyv and concurrently introducing successive portions of ketene and dry hydrocyanic acid into a solution in an anhydrous volatile solvent for the ketene and hydrocyanic acid of a basic catalyst for the resultant condensation between the ketene and hydrocyanic acid, which catalyst does not substantially react with ketene to form non-basic reaction products under the conditions of the said condensation reaction, while maintaining said tion mixture at least one of the resultant reac-- tion products selected from the group consisting of l-cyanovinyl acetate and dimolecular acetyl cyanide.

8. Process which comprises slowly and concurrently introducing successive portions of ketene and dry hydrocyanic acid in the ratio of between 2 and 3 mols of the ketene per mol of the said acid into a solution of a tertiary amine in an anhydrous volatile solvent for the ketene and hydrocyanic acid, said solution being maintained at a temperature within the range between about --50 C. and about (2., and separately recovering from the resultant reaction mixture at least one of the resultant reaction products selected from the group consisting of l-cyanovinyl acetate and dimolecular acetyl cyanide.

9. Process which comprise slowly and concurrently introducing successive portions of ketene and dry hydrocyanic acidin the ratio of between 2 and 3 mols of the ketene per mol of the said acid into a solution of a quaternary ammonium base in an anhydrous volatile solvent for the ketene and hydrocyanic acid, said solution being maintained at a temperature within the range between about -50 C. and about +30 0., and separately recovering from the resultant reaction mixture at least one of the resultant reaction products selected from the group consisting of l-cyanovinyl acetate and dimolecular acetyl cyanide.

10. Process which comprises slowly and con currently introducing successive portions of ketene and dry hydrocyanic acid in the ratio of between 2 and 3 mols of the ketene per mol of action products selected from the group consisting of l-cyanovinyl acetate and dimolecular acetyl cyanide.

FRANmIbT JOHNSTON. LAWRENCE W. NEWTON. 

